Method for operating a pre-crash sensing system to deploy airbags using inflation control

ABSTRACT

A method of operating a restraint system comprises deploying an airbag in response to a pre-crash sensing system prior to collision in a first stage and controlling an inflation of the airbag in a second stage in response to acceleration signals of the vehicle.

TECHNICAL FIELD

The present invention relates to pre-crash sensing systems forautomotive vehicles, and more particularly, to pre-crash sensing systemsthat determine an imminent crash and may deploy an airbag prior tocrash.

BACKGROUND

Auto manufacturers are investigating radar, lidar, and vision-basedpre-crash sensing systems to improve occupant safety. Pre-crash sensingsystems have been recognized to have the potential of improving occupantsafety by deploying the passive restraint devices earlier in a crash, oreven before the actual impact. This extra time allows more flexibilityfor component design and can allow the passive restraints system to beindividually tailored to the occupant and crash scenario.

Current vehicles typically employ accelerometers that measuredecelerations acting on the vehicle body in the event of a crash. Inresponse to acceleration signals, airbags or other safety devices aredeployed. The pre-crash sensors also sense information before impactconcerning the size, relative path, object classification and closingvelocity of the object, which cannot be calculated by conventionalaccelerometer-based sensors until after the crash. In certain crashsituations it would be desirable to provide information before forcesactually act upon the vehicle when a collision is unavoidable. Thepre-crash sensing systems that exist today are significantly morecomplex than the accelerometer based systems, both in hardware andalgorithm complexity, because the pre-crash system must predict impactseverity prior to actual contact.

Remote sensing systems using radar, lidar or vision based technologiesfor adaptive cruise control, collision avoidance and collision warningapplications are known. These systems have characteristic requirementsfor avoiding false alarms. Generally, the remote sensing systemreliability requirements for pre-crash sensing for automotive safetyrelated systems are more stringent than those for comfort andconvenience features, such as adaptive cruise control. The reliabilityrequirements even for safety related features vary significantly,depending upon the safety countermeasure under consideration. Forexample, tolerance towards undesirable activations may be higher foractivating motorized seatbelt pretensioners, also calledelectro-mechanical retractors (EMR), than for functions such as vehiclesuspension height adjustments. Non-reversible safety countermeasures,including airbags, require extremely reliable sensing systems forpre-crash activation.

Redundant sensors are necessary in order to achieve long-range targettracking, while also providing accurate short-range information about animpact-imminent target. Furthermore, the algorithms that have beendeveloped to detect objects and imminent collisions are required to meetvery high reliability requirements for deploying non-reversible passiverestraints devices (e.g. airbags). Given the complexity of the pre-crashsensing signal, along with the required fusion of targets from multiplesensors, often employing different technologies for sensing, such highreliability has not yet been achieved. Thus, to date, all applicationsof pre-crash sensing to restraints have been limited to eitherpre-arming of non-reversible restraints (e.g. airbags), or deploying ofreversible restraint devices (e.g. electro-mechanical seatbeltpretensioners).

It would therefore be desirable to provide a pre-crash sensing systemthat provides accurate determinations as to the presence of a potentialcollision target for pre-activation of non-reversible restraints,pre-arming of non-reversible restraints, and for deployment ofreversible restraints.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of a host vehicle relative to a crash objectaccording to the present invention.

FIG. 2 is a top view of a host vehicle illustrating the various exteriorviews and a simple block diagrammatic view of the occupant sensingsystem and a restraint control module.

FIG. 3 is a block diagrammatic view of the system according to thepresent invention.

FIG. 4 is a block diagrammatic view of the controller 52 of FIG. 3.

FIG. 5 is a flow chart of a first embodiment illustrating a method foroperating the present invention for frontal collision occupantprotection.

FIG. 6 is a plot illustrating various airbag pressures versus time forthe timing of deployment of airbags.

FIG. 7 is a flow chart illustrating a method for operating a driverairbag vent system.

FIG. 8 is a plot of speed versus time of various collisions so thatvarious timings may be determined.

FIG. 9 is a flow chart illustrating a method for operating a ventaccording to the present invention.

FIG. 10 is a flow chart illustrating a method for operating a pre-crashsensing system according to another embodiment of the invention.

FIG. 11 is a plot of pressure versus time of various modes for inflatingan airbag.

FIG. 12 is a plot of confidence level versus time for various types ofrestraint activations.

FIG. 13 is a plot of the deployment of various restraints based uponestimated time, collision confidence levels, and collisioncharacteristics.

FIG. 14 is a plot of software for a deployment handler.

FIG. 15 is a block diagrammatic view of decisions determined by adeployment handler.

FIG. 16 is a method for operating restraints according to an embodimentof the current invention.

FIG. 17 is a flow chart illustrating the stage 1 determination of FIG.14.

FIG. 18 is a flow chart illustrating the deployment logic of an airbagigniter according to an embodiment of the current invention.

SUMMARY OF THE INVENTION

The present invention provides an improved pre-crash sensing system.

In one aspect of the invention, a method of operating a restraint systemcomprises deploying an airbag in response to a pre-crash sensing systemprior to collision in a first stage and controlling an inflation of theairbag in a second stage in response to acceleration signals of thevehicle.

In a further aspect of the invention, a method of operating an airbaghaving a controllable vent comprises deploying an airbag, determining acrash severity, determining occupant information, and operating anairbag vent in response to crash severity and the occupant information.

One advantage of the invention is a more accurate determination of thecrash conditions and the occupant status, which may be used to predeploythe airbag and provide an incremental safety benefit for the occupants.

Another advantage of one embodiment of the invention is that by havingcontrollable vents, the uncertainty of calculations in predeployment maybe compensated for by using actual acceleration signals after acollision occurs. That is, predeployment is based upon forecasts of acollision and uncertainty in such a calculation may then be compensatedfor due to the certainty of a collision as sensed by accelerationsensors.

Other advantages and features of the present invention will becomeapparent when viewed in light of the detailed description of thepreferred embodiment when taken in conjunction with the attacheddrawings and appended claims.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In the following figures the same reference numerals will be used toidentify the same components. While the present invention is illustratedwith respect to several types of pre-crash sensors, various types andcombinations of pre-crash sensors may be used as will be furtherdescribed below.

Referring now to FIG. 1, a host vehicle 10 is illustrated with respectto a crash object such as another vehicle 12. The host vehicle 10includes an object or pre-crash sensor 18 that is coupled to an airbagor other restraint control module (RCM) 20. In addition, an optionalmechanical contact sensor 22 is shown protruding from the front of thevehicle. In response to the pre-crash sensor 18, the RCM 20 may activatean airbag or other restraints within the vehicle as will be furtherdescribed below. As is described below the vehicles 10 and 12 are atfull overlap. If only half of the vehicle 10 were going to be hit (thiswould be a 50% offset). This would be illustrated by moving vehicle upor down on the figure.

Referring now to FIG. 2, the host vehicle 10 is illustrated in furtherdetail. The host vehicle 10 is shown having the restraint or airbagcontrol module, RCM, 20 therein. The restraint control module 20 may becoupled to lateral accelerometers 24 disposed on both sides of thevehicle. Also, longitudinal accelerometers 26 may be provided near thefront of the vehicle 10. An accelerometer housing 28 having alongitudinal accelerometer positioned near the center of gravity of thevehicle may also be provided. A lateral accelerometer may also bepositioned at the physical center of the vehicle floor within housing28.

FIG. 2 illustrates various mechanical contact sensors 22 positioned atvarious locations around the vehicle. This is an optional confirmingfeature not required by the embodiments of the present invention.

The pre-crash sensor 18 is illustrated having a range of view for avision system 30, a field of view 31 for a laser system and a range ofview for a radar system 32. Front, rear, and right and left side rangesof views for the vision and lidar/radar systems are illustrated.

Vehicle 10 may also include an occupant sensing system 36 that includesoccupant sensors 38. The occupant sensors 38 may include various typesof sensors including sensors that determine the weight, volume, and/orposition of the occupants within the vehicle.

Referring to FIG. 3, a pre-crash safety system 50 has a controller 52.Controller 52 is preferably a microprocessor-based controller that iscoupled to a memory 54 and a timer 56. Memory 54 and timer 56 areillustrated as separate components from that of controller 52. However,those skilled in the art will recognize that memory 54 and timer 56 maybe incorporated into controller 52.

Memory 54 may comprise various types of memory including read onlymemory, random access memory, electrically erasable programmable readonly memory, and keep alive memory. Memory 54 is used to store variousthresholds and parameters as will be further described below.

Timer 56 is a timer such as a clock timer of a central processing unitwithin controller 52. Timer 56 is capable of timing the duration ofvarious events as well as counting up or counting down. For example,based on time the velocity of the vehicle can be determined from anacceleration.

A remote object or pre-crash sensor 18 is coupled to controller 52.Pre-crash sensor 18 generates an object signal in the presence of anobject within its field of view. Pre-crash sensor 18 may be comprised ofone or a number of types of sensors including a radar 62, a lidar 64,and a vision system 66. Vision system 66 may be comprised of one or morecameras, CCD, or CMOS type devices. As illustrated, a first camera 68and a second camera 70 may form vision system 66. Both radar 62 andlidar 64 are capable of sensing the presence and the distance of anobject from the vehicle. When used as a stereo pair, cameras 68 and 70acting together are also capable of detecting the distance of an objectfrom the vehicle. In another embodiment of the invention vision systemconsisting of cameras 1 and 2 alone may use established triangulationtechniques to determine the presence of an object and the distance fromthe vehicle as well as the object's size that may include area, heightor width, or combinations thereof. The cameras are may be high-speedcameras operating in excess of 100 Hz. A suitable example is aCMOS-based high dynamic range camera capable of operating under widelydiffering lighting and contrast conditions. Finally, as will be furtherdescribed below, radar 62, lidar 64 and/or vision system 66 may be usedto detect an object and the mechanical contact sensor 22 may be used toconfirm the presence of the object and to provide the stiffness of theobject to controller 52.

A receiver 91 may also be included within pre-crash sensor 18. Thereceiver 91 may, however, be a stand-alone device. Receiver 91 is alsocoupled to controller 52.

A vehicle dynamics detector 72 is also coupled to controller 52. Thevehicle dynamics detector 72 generates a signal or signals indicative ofthe dynamic conditions of the vehicle. The vehicle dynamics detector 72may comprise various numbers or combinations of sensors but preferablyinclude a speed sensor 74, a yaw rate sensor 76, and a steering wheelangle sensor 78.

Speed sensor 74 may be one of a variety of speed sensors known to thoseskilled in the art. For example, a suitable speed sensor may include asensor at every wheel that is averaged by controller 52. Preferably,controller 52 translates the wheel speeds into the speed of the vehicle.Suitable type of speed sensors 74 may include, for example, toothedwheel sensors such as those employed on anti-lock brake systems.

Yaw rate sensor 76 preferably provides the yaw rate of the vehicle aboutthe center of gravity of the vehicle. The yaw rate measures therotational tendency of the vehicle about an axis normal to the surfaceof the road. Although yaw rate sensor is preferably located at thecenter of gravity, those skilled in the art will recognize that the yawrate sensor may be located in various locations of the vehicle andtranslated back to the center of gravity either through calculations atthe yaw rate sensor 76 or through calculations within controller 52 in aknown manner.

Steering wheel angle sensor 78 provides a steering wheel angle signal tocontroller 52. The steering wheel angle signal corresponds to thesteering wheel angle of the hand wheel of the automotive vehicle.

A global positioning system (GPS) 96 may also be coupled to controller52. GPS system 96 generates a position of the host vehicle 10 inresponse to satellite signals. Controller 52 may use this information indetermining the dynamics of the host vehicle.

A transponder 98 may also be coupled to controller 52. Transponder 98may generate information from controller 52 and transmit it to othervehicles upon the reception of a predetermined frequency signal fromanother vehicle. Also, transponder 98 may always be activated andbroadcasting vehicle information to other vehicles. Transponder 98 andreceiver 91 may be located in a common location and integrally formedtherewith.

Controller 52 is used to control the activation of a countermeasuresystem 100. Each countermeasure may have an individual actuatorassociated therewith. In that case, controller 52 may direct theindividual countermeasure actuator to activate the countermeasure.Various types of countermeasure systems will be evident to those skilledin the art. For various devices the restraint control module 20 may becontrolled. Examples of a countermeasure within countermeasure systeminclude seatbelt retractors 101, seatbelt belt pretensioners 102, frontinterior airbags 104, side curtain airbags 106, exterior or pedestrianprotection airbags 108, knee bolsters 110, bumper height changing 112including nose dipping, braking 114, and other measures 116 such as butnot limited to steering column position, seat position and windowclosure. Preferably, controller 52 is programmed to activate theappropriate countermeasure in response to the inputs from the varioussensors. As will be described below, the controller may choose thecountermeasure based on the type, orientation, classification, andstiffness of the collision object.

Referring now to FIG. 4, a portion of controller 52 and a portion of therestraint control module 20 are illustrated in further detail.Controller 52 has an object classifier 202 therein. Object classifier202 may be implemented in hardware or software. Object classifier 202may be used to provide an object orientation and an objectclassification to an impact prediction module 210. Although objectclassifier 202 is illustrated as part of controller 52, objectclassifier 202 may be part of vision system 66 or pre-crash or objectsensor 18. Object classifier 202 may compute various information basedon the images received. For example, the shape and feature-based metricsmay be used for potential collision assessment and countermeasureactivation decisions. Vehicle features may include but are not limitedto ground clearance, tire profiles, tire size, tire separation distance,the number of tires, height and width of the object, a cross-sectionalcontour of the vehicle including engine compartment, passengercompartment, and trunk or truck bed area, presence of bumpers, bumperheight, front and rear license plates, front and rear lighting fixtures,front and rear lights, front grill, front and rear windshield wipers,exterior mounted spare tire, sideview mirrors, B and C pillar lines,towing gear, wheel well profiles, steering wheel profiles, humanpassenger profiles, relative positioning of the objects, rear axle andexhaust systems. Typically, the target vehicle information will bemaintained over time until an accurate classification can be determined.Object classifier 202 may also be fuzzy logic-based.

The controller 52 combines the information such as object distance,azimuth position, relative velocity, relative acceleration, objectclassification, and orientation, and other host vehicle information fromthe vehicle dynamics detector 72 such as speed, yaw rate, and steeringwheel position to deploy the appropriate actuator. The controller 52utilizes the sensor inputs and based on rules deploys safety systemsonly to the extent that it is required according to the sensedcondition, vehicle dynamics, and compatibility with the other vehicle.The controller 52 may also use near-zone sensing from sensors such as aradar/lidar sensor, transponder, and global positioning system toimprove the reliability and robustness of the pre-crash sensingdecisions. The controller 52 may be a stand-alone processor or part ofanother vehicle system.

The radar of the pre-crash sensors 18 identifies longer range targetsand can compute their azimuth angle, size, range and range rate. Thecameras 68, 70 may be used for classification of objects into vehicle,non-vehicle, pole, etc. The lidar 64 computes close range closingvelocity and separates targets into multiple detection zones. Forexample, the detection zones may correspond to driver side, central, orpassenger side zones. The data from the object classifier 202, thepre-crash sensors 18, and the contact sensors 22 are coupled to impactprediction block 210. The data from the various sensors are fusedtogether, preferably in software, to provide an impact prediction forthe rest of the system and allows the confirmation of the targets frommultiple sensors. The prediction calculation may also include aconfidence level calculated by using time-in-view, pattern matching, andthe like, to provide a metric defining a confidence of the predictedcollision. A path crossing impact such as at traffic intersections maynot be in view long enough to calculate a reliable impact. Vision andlaser sensors also have inherent limitations such as fromenvironment-related conditions. For these reasons, the pre-crash sensorsand corresponding software-based predictions are combined withadditional sensor-based predictions to achieve the needed reliabilityfor restraint system deployment before collision. When the confidencelevel is not sufficient to predeploy or pre-arm the irreversiblerestraints, the restraints may be deployed conventionally using theaccelerometer output in a conventional manner.

Due to the probabilistic nature of remote sensor-based pre-crashcollision predictions due to the limitations of the sensors describedabove, it may be desirable to provide a more reliable confirmation suchas a protruding contact sensor 22.

The pre-crash sensors 18 provide impact time, confidence, range, rangerate, azimuth angle, and the object classifier 202 provides an objectclassification. The protruding contact sensors 22 may provide contactsensor location information and a force profile provided from thecontact sensor. Accelerometers 24, 26 and 28 provide variousaccelerations such as longitudinal and lateral accelerations. The impactprediction block 210 is coupled to a driver restraint control algorithm220 and a passenger restraint control algorithm 222. Interior sensors 38are also coupled to driver restraint control algorithm 220 and passengerrestraint control algorithm 222. The interior sensors 38 provide variousinformation such as the driver belt buckle status and driverclassification. The driver classification may be based upon weight andrange. The range may include which percentile the occupant is in, theposition of the seat, and the driver belt buckle status. Thus, interiorsensors provide information about the occupants so that proper restraintdeployments may take place. The impact prediction block 210 providesactive countermeasure status, the impact mode, impact speed, and objectclassification to the driver restraint control algorithm 220 and thepassenger restraint control algorithm 222. The driver restraint controlalgorithm 220 is coupled to driver restraint actuators 224 and thepassenger restraint control module 222 is coupled to the passengerrestraint actuators 226. The driver restraint actuators and passengerrestraint actuators receive information about the deployment of thevarious devices including a seatbelt load limiter, airbag stage 1inflator, airbag stage 2 inflator, airbag venting, electromechanicalretractor (i.e. motorized seatbelt pretensioner), and seatbeltpyro-pretensioner. The driver and passenger restraint control algorithmsgenerate various timings for these devices.

Referring now to FIG. 5, a method of operating the present inventionstarts in block 300. In block 302, the host vehicle state is monitored.The monitoring may take place with vehicle dynamics detector 72,protruding contact sensors 22, accelerometers 24, 26 and 28 and variousother sensors of the vehicle. In step 304, the driver and passengerseatbelt status is determined. In step 306, the driver and front seatpassenger are classified into occupant classes such as their weightcategory and position. In step 308, the frontal zone of the vehicle isscanned with the pre-crash sensing system. In step 310, the relativevelocity and potential collision threat is assessed. In step 312, thepotential collision is classified. Various types of classification maytake place including a full frontal collision, an offset collision, acollision with a rigid barrier, the type of object into which thevehicle may be colliding, and the like. Various types of collisions maycall for a predeployment. In step 314, if the collision classificationcalls for predeployment, step 316 is implemented. In step 316, thedriver and/or passenger airbag are deployed in a pre-collision mode. Instep 314 if no pre-collision is desired step 302 is again performed.

In step 326 the vehicle acceleration sensors are monitored. After step326, step 327 determines if the collision has been confirmed with thevehicle-mounted accelerometers within time-to-collision plus a tolerancevalue. In step 327, if a collision has not been confirmed by theaccelerometers, step 330 is implemented in which active vents areactivated based on severity, occupant information and predicted impacttime. In step 327, if the vehicle collision has been confirmed, step 328is implemented in which the predicted impact time is adjusted based onthe data from the accelerometers (detailed in FIG. 8). After adjustingthe predicted impact time, step 330 is implemented as explained above.In step 340, the system ends.

Referring now to FIG. 6, airbag inflators and active vents may becontrolled in various ways. In FIG. 6, 40 ms, 20 ms, 0 ms before contactand 9 ms after contact airbag inflator activation stages areillustrated. As can be seen, in the −40 ms time frame, the airbaginflator is activated about 40 ms prior to impact in response to thevarious vehicle inputs. The vents open at a predetermined time to allowthe airbag to be filled as predetermined so occupant contact happenswith a properly pressurized airbag. A pressure plot from an airbagactivated 20 ms prior to contact is also illustrated with a ventopening, initial bag contact, and steering column stroke ends.

Referring now to FIG. 7, a method for controlling a driver airbag ventis illustrated. Those skilled in the art will recognize that apassenger-side airbag may be controlled in a similar manner. In step400, the determination of the driver airbag vent is started. In step402, an airbag wait time, an airbag deployment flag, driver size, beltbuckle status, and driver seat track position may all be considered inthis determination. Those skilled in the art will recognize additionalor fewer determinations may be used. In step 404, if the airbagdeployment is met, a restraint level is returned from a restraint leveltable in step 406. A vent delay time 408 is returned according to theparameters in step 402. The vent delay time may take into considerationvarious design constraints of the vehicle. Thus, the table isexperimentally determined at the time of vehicle development based onthe configuration of the vehicle. The vent delay time may be determinedin various manners. In step 410, the delay timer is started. In step412, if the vent delay time plus the airbag wait time is less than thedelay time from step 410, the delay timer is incremented in step 413,and step 412 is executed again. In step 412, if the vent delay time plusthe airbag wait time is greater than or equal to the delay time fromstep 410, step 414 is executed in which the airbag vent is deployed.Step 416 is executed stopping the method after step 414.

FIG. 8 shows the reduction in vehicle speed for various impactconditions: 30 mph 100% Overlap Barrier, 35 mph 100% Overlap Barrier, 40mph 40% Offset Deformable Barrier, and 48 mph 25% Overlap Car-Carcollisions. These curves can be obtained by processing the accelerometersignals from the vehicle accelerometers. For the proper activation ofactive vents, it is highly desirable to accurately determine collisioncontact initiation time. The vehicle speed curves may be filtered andcurve fit to produce trend lines 480. These trend lines are related tothe vehicle-specific contact initiation time, which may be used as areference point for the airbag vent deployment time.

Referring now to FIG. 9, a method is illustrated for controlling theactive vent deploy times of an airbag. The values listed here are forillustrative purposes. In step 502, the variables are initialized.V₁=V₂=V_(F1)=V_(F2)=V_(RCM)=V_(el)=N_(array)=T_(N)=M=B=D=Vel_(array)=0.V_(thresh)=0.25 m/s. T_(x)=T_(veh)=3 ms. T_(end)=6 ms.Min_filtered_points=4, Vel_max_point=T_max_point=N_max_point=0,tol_B=250 m/s² and T_(Deploy)=999.9. In step 504, the accelerationvalues from the RCM and the front accelerometers are recorded. In step505, the restraint level and the activation time of the vent (T_(vent))is returned to the present sub-routine. In step 506, the front crashsensor and RCM accelerations are integrated and produce velocities:V_(F1), V_(F2), and V_(RCM). In step 507, V_(RCM) is subtracted fromV_(F1), and V_(F2), so vehicle-wide accelerations, i.e. braking, willnot be interpreted as impact acceleration. In step 508, V₁ is comparedagainst a threshold velocity, V_(thresh). If V₁ is less than toV_(thresh), then step 518 is activated. Step 518 compares V2 againstV_(thresh) so that if neither V1 nor V2 are above V_(thresh), then thealgorithm returns to step 504, through step 519. Step 519 increments thealgorithm time by the time step (time_step) used by processor. In steps510, 512, 514, and 516, the largest value between V₁ and V₂ is chosenfor Vel. Once the Vel and D variables are updated in step 514 or 516,then step 520 is activated, and the array counter is increased by oneand the algorithm time is incremented by time_step. Step 521 stores thelatest value for N_(array) and T_(N) in the appropriately named arrays.In step 522, the latest point in Vel_(array) is compared against theprevious maximum velocity in the array (Vel_max_point). If the latestpoint in Vel_(array) is greater than Vel_max_point, then velocity(Vel_max_point), time (T_max_point), and counter (N_max_point) areupdated with the value of the latest information in step 523. After anegative return from step 522 or after step 523, step 524 is active. Instep 524, the overall time length of the array(T_(array)[Narray]−T_(array)[1]) is compared to a threshold end time(T_(end)) for the array. If the overall time length of the array is lessthen the threshold end time, then the method proceeds to step 525. Instep 525 the accelerations are recorded. In step 526 the accelerationsare integrated and V_(F1), V_(F2), and V_(RCM) are returned. In step527, Vel is updated with the latest data point from the accelerometeridentified by D. The method then proceeds to step 520 as describedabove.

If the overall time length of the array is greater than or equal to thearray's threshold end time, then the method continues to step 530. Instep 530, a linear regression is performed on Vel_(array) to provide alinear equation of the form y=M*x+B. In step 531, the equation'sx-intercept is calculated and saved in a variable named T_(x). In step532, the minimum value in Vel_(array) is compared against V_(thresh). Ifthe operation in step 532 returns a true result, the method proceeds tostep 550. In step 550 the T_(zero) time calculated using pre-crashsensor data is returned. If step 532 returns a false result, the methodproceeds to step 533. Step 533 compares the number of points in thefiltered array (N_max_point) to a minimum threshold value(min_filtered_points). If N_max_point is greater than or equal to theminimum number of points, then step 534 is activated. If the number ofpoints is less than the threshold, then step 540 is activated. In step534, the slope of the linear regression line (B) is compared against athreshold slope value (tol_B). If B is greater than or equal to thethreshold slope value, then step 535 is activated, otherwise step 540 isactivated. In step 535, the T_(zero) time is calculated based on theintercept time (T_(x)) calculated in step 531 and a vehicle-specifictime offset (T_(veh)). After completion of step 535, 540 or step 550,step 560 is activated. In step 560, the airbag vent is deployedaccording to the T_(zero) time and the T_(vent) time returned from step505. Step 570 is executed stopping the method after step 560.

Referring now to FIG. 10, a method of operating a restraint system isset forth. In this system the confidence levels are determined. In thissystem, steps 600-612 are identical to steps 300-312 of FIG. 5 and thuswill not be repeated. In step 614, if the collision classification callsfor predeployment, step 618 is executed. In step 618, the relativevelocity is determined. If the relative velocity is between 15 and 100mph, step 620 is executed. In step 620, if the confidence factorthreshold is met for preactivation, step 624 is executed. In step 624,the adaptive restraints are deployed in pre-collision mode. In 625 thesystem ends. Referring back to steps 614, 618 and step 620, if thecollision classification or relative velocity does not call forpredeployment or the confidence factor is not met, step 626 is executed.In step 626 a collision is confirmed with the accelerometers. In step627, if the collision is not confirmed, step 602 is executed. In step627, if the collision is confirmed, the adaptive restraint system isdeployed in a post-collision mode in step 630. In step 640 the systemends.

Referring now to FIG. 11, in the specific case of an airbag deployment,if deployed pre-impact there is sufficient time to reduce the risk ofinjuries to Out-Of-Position occupants by slowing the inflation of theairbag. If it is deployed post-impact, the airbag must be able toinflate quicker in order to be positioned for occupant restraint beforecontact with an in-position occupant. One airbag design that couldachieve this is a conventional two-stage inflator with a controllabledelay between the two stages combined with an adjustable venting toallow control of the airbag inflation characteristics. The airbag outputcould then be controlled in many ways including the following.

Mode 1 illustrates a slow deployment which consists of a low pressure atthe onset of deployment. The slow deployment is enough to guaranteeopening of the airbag cover door. The airbag vents are closed duringthis early stage of deployment in order to collect the maximum amount ofgas at the onset of inflation. Once the bag is through the airbag doorand is appropriately positioned, the inflator output increases to fillthe bag and vents may open to dissipate the occupant's kinetic energy.The peak pressure of the airbag would be equivalent to the maximumpressure of the current production airbag. The entire process isdesigned to occur over an extended time period relative to conventionalsystems, which are listed below in modes 2 and 3.

In mode 2, a conventional full output that is roughly equivalent to bothstages of current production two-stage airbags is illustrated. In thismode the airbag vents are open from the beginning and both stages deploywith a small or even no delay between the two inflator stages. The peakpressure of the bag is roughly equivalent to the peak pressure in mode 1but it may be achieved in a shorter time.

In mode 3, a conventional partial output is roughly equivalent to thefirst stage of the current production two-stage airbag. In this mode theairbag vents are open from the beginning. Both inflator stages deploywith a large (about 100 ms) delay between the first and the second stagewith a lower peak pressure.

Using this airbag pre-deployment method, the airbag may be inflated to apeak pressure that will provide sufficient protection to full sizeoccupants while reducing injury to an occupant situated too close to theairbag at the time of deployment. Other components such aselectro-mechanical retractors (EMR), load limiters and the like may beoperated in pre-impact mode or post-impact mode in order to providemaximum protection in various conditions.

Referring now to FIG. 12, an embodiment that is based upon theprediction collision confidence levels and the deployment timerequirements for maximum effectiveness is determined. As illustrated,conventional restraints are activated between 5 ms after impact and 120ms after impact. In the second line from the bottom, reversiblerestraint preactivation may take place up to 250 ms before impact. Inthird line, pyrotechnic pretensioner preactivation may take placebetween −10 ms and 120 ms. Partial airbag preactivation may take placebetween −20 ms and 120 ms and full airbag preactivation may take placebetween −40 ms and 120 ms. When the confidence level is low, reversiblerestraints may be activated with no major implications to the vehicleoccupants, if a collision does not occur. Pyrotechnic pretensioners maybe activated with a medium level of confidence. A higher level ofconfidence is required for full preactivation of an airbag. The time tocollision and collision confidence levels are based upon the pre-crashsensor 18, vehicle dynamics detector 72, and the mechanical contactsensor 22.

Referring now to FIGS. 13A and 13B, step 700 starts the system. In step702, the vehicle surroundings are monitored for potential collisionswith the pre-crash sensing system. In step 704 the interior of thevehicle is monitored and the occupant characteristics determined. Instep 706, if a potential collision is not detected the system returns tostep 702. In step 706, if a potential collision is detected, the time tocollision, collision confidence level, and collision characteristics maybe determined, 708. In step 710, the collision confidence level anddeployment time requirements for reversible restraints pre-activationare checked. If the confidence level and deployment time requirementsfor the pre-activation are not met, step 702 is again executed. In step710 if the confidence level and deployment time requirements for thepre-activation of reversible restraints are met, step 712 deploys thereversible restraints.

In step 714, the vehicle surroundings are continually monitored for apotential collision. In step 716, a time to collision, collisionconfidence level, and collision characteristics are again determined. Instep 718, the collision time and collision confidence level are comparedto multiple deployment thresholds for pre-activation of non-reversiblerestraints. In step 719, if the confidence level and deployment timingrequirements for full deployment of airbags before collision are met,step 720 is executed in which the airbags and other non-reversiblerestraint devices are started before the impact based upon the collisioncharacteristics and occupant characteristics. Referring back to step719, if the confidence level and deployment time requirements for fulldeployment of the airbags before a collision are not met, step 722 isexecuted. In step 722, if the confidence level and deployment timingrequirements for partial deployment of airbags before collision are met,step 724 partially deploys the airbags and other non-reversiblerestraint devices before impact based upon collision characteristics andoccupant characteristics. After step 724, step 726 is executed. In step726, if impact is detected by the contact sensors with severity over apredetermined threshold, step 727 completes the deployment of the safetydevices. If in step 726 the impact severity detected by the contactsensors is not over a threshold value, step 728 is executed in which thetime elapsed is compared with the predicted time for collision. If thetime elapse is not equal to or greater than the predicted time forcollision, step 726 is again performed. In step 728, if the time elapsedis equal to or greater than the time predicted for collision, step 730is performed in which the deployment is stopped and the inflated safetydevices are vented. In step 732, the reversible restraints are reversed.In step 734, the system returns to start in step 700.

Referring back to step 722, if the confidence level and deployment timerequirements for partial deployment of airbags before collision are notmet, step 740 is executed in which the confidence level and deploymenttiming requirements for activating pyro-pretensioners before thecollision are determined. If the confidence levels for activatingpyro-pretensioners before collision are met, step 742 is executed inwhich the pyro-pretensioners are activated before collision. In step740, if the confidence levels for activating pyro-pretensioners beforecollision are not met, step 744 is executed in which a collision withimpact-based sensors is determined. If a collision is detected withimpact-based sensors over a threshold, step 746 deploys airbags andother non-reversible restraint systems based upon impact-based collisioncharacteristics and occupant characteristics.

Referring back to step 744, if collision as detected by impact sensorsis not over a threshold, the time elapsed is compared with the timepredicted for collision. If the time elapsed is equal to or greater thanthe time predicted for collision the reversible restraints are reversedin step 750 and the system returns to start in step 734. In step 748, ifthe time elapsed is not equal to or greater than the time predicted,then step 752 is executed. In step 752, the system returns to step 714and the process repeats.

Thus, as can be seen, maximum benefits of pre-collision activation ofrestraint systems are realized when the airbag is fully activated beforea collision. For full airbag deployment before collision, the highestlevel of collision prediction confidence level is required, at a presettime (for example, at −40 ms) before a predicted collision. In thiscase, the restraint system including the airbags, pyrotechnic seatbeltpretensioners and other safety devices may be deployed based uponcollision classification, collision severity. and occupant informationwithout additional constraints on airbag deployment. This providesoptimal occupant protection. If the predefined collision predictionconfidence level is not met, airbag deployment decision may be delayedto the next best situation, namely that of partial airbag deploymentbefore a predicted collision. At a predetermined time before thepredicted collision, which is later than in the case of a full airbagdeployment decision (for example, −20 ms), a deployment decision is madefor partial deployment of the airbag if a predefined high collisionprediction confidence level is noted. This partial airbag predeploymentconfidence level is set lower than the full airbag pre-deploymentconfidence level. In this situation the control algorithm has extra timeand additional pre-crash sensor data to make new collision predictionconfidence calculations. In the case of partial airbag deployment beforecollision, typically only the low output stage of a two-stage airbag maybe generated and pyrotechnic pretensioners are predeployed. The highoutput stage is initiated only after collision confirmation based uponcontact sensors. After the collision is confirmed by the contact-basedsensors, the high output stage of the airbag, and other restraintcontrol mechanisms such as active vents are activated in a controlledmanner in accordance with the collision severity, collisionclassification, occupant information, belt status, low stage airbagstatus, and the like. In the rare event that a collision is avoided orthe collision is of minor severity, the deployment of the high outputstage of the airbags may be avoided. If the preset high collisionconfidence level for partial airbag deployment is not met by thepredetermined time, no deployment decision may be made. At a laterpredetermined time (about −10 ms) the decision may be made whether todeploy pyrotechnic pretensioners. This is based upon a predefinedmedium-high collision confidence level which is preset to be lower thanthat needed for partial pre-collision deployment of airbags. Thesepyrotechnic devices cannot be reversed and must be replaced afterdeployment. In this case the airbag deployment may be controlled by thecontact based sensor information such as the accelerometers with a viewtoward the seatbelt status including the electro-mechanical retractor(EMR) and pyrotechnic pretensioner status and various occupantinformation.

If the predetermined medium-high collision prediction confidence levelis not met by the predetermined time, the system allows conventionalimpact-based collision sensing system to control the restraint systemdeployment function based upon predicted collision severity, beltstatus, including pretensioner status and occupant related information.

Referring now to FIG. 14, a deployment handler according to the presentinvention is illustrated. In this example there are five controlvariables, namely, electro-mechanical seatbelt retractor activationtime, airbag stage 1 activation time, airbag stage 2 activation time,pyrotechnic seatbelt activation time and active vent opening time. Thesetimes are selected to optimize the restraint system performance. Thesoftware associated with the deployment handler receives informationfrom the active safety system 800 and provides this information to afirst stage, a deployment determination stage 802. A device activationstage 804 receives various information from the deployment determinationstage 802. It should be noted that in the prior examples and in theexamples set forth herein, the various times are by way of example onlyand are not meant to be limiting. Timing may be adjusted for variousreasons including the types of devices to be deployed and the vehicledesign.

The active safety system generates a predicted impact time, an impactrelative speed, an impact probability, an impact overlap, an impactangle, impact sensor detection, and impact maturity detection signalsthat are provided to the deployment determination 802. As mentionedabove, various times may be used for certain devices such as if theimpact time is less than 40 ms an airbag activation decision may bedetermined. If the impact time is less than 250 ms theelectro-mechanical retractor (EMR) may be used to retract the seatbelt.Impact probability, impact overlap, impact angle, impact sensordetection and impact maturity detection may also be used for deploymentdecision. The maturity detection greater than two means that a targethas been detected for more than two radar cycles. The deploymentdetermination 802 generates an impact relative speed, an airbagdeployment met signal, an airbag wait time, an electro-mechanicalretractor deployment met signal, and an electro-mechanical retractorwait time signal to the device activation stage 804.

In box 804, the device activation stage may perform various functionsand set forth various timings based upon the information received fromthe deployment determination and an occupant size signal, seatbelt usagesignal and seat position signal. Examples of timing for a large occupantare illustrated.

For the first function for a belted large occupant, EMR is deployed at−250 ms, airbag stage 1 is deployed at −20 ms, airbag stage 2 at −40 ms,airbag vented at −25 ms, and a pyrotechnic belt pretensioner is deployedat −40 ms. As can be seen, the airbag stage 2 was deployed before thefirst stage. For an unbelted large occupant the airbag stage 1 may bedeployed at −40 ms, airbag stage 2 at 0 ms, and airbag venting at −25ms.

Another function performed by the device activation is determining astart time for a clock. The clock may have a wait time and set thedeployment of the EMR at −250 ms, the second stage airbag at −40 ms,deploy pretensioners at −40 ms, the airbag venting at −25 ms, and airbagstage 1 at −20 ms corresponding to the situation for a large beltedoccupant. As mentioned above, these are merely examples of activationsof various devices. It should be noted that the above two functions aredescribed by the way of example only and are not meant to be limiting.Those skilled in the art will realize that the device activation stagecontains similar additional functions for other size occupant underbelted and unbelted conditions in driver and passenger positions.

In summary, the device activation may generate an airbag stage 1 signal,an airbag stage 2 signal, and airbag venting signal, a seatbeltpyrotechnic pretensioner signal, and a seatbelt retractor signal.

Referring now to FIG. 15, a graphical representation of a deploymenthandler scheme is illustrated. In block 900 the closing velocity isdetermined. In block 902 the collision type such as a collision with asedan front, sedan rear, Sports Utility Vehicle (SUV) front, SUV rear isdetermined. Of course, various other classifications may be determined.A collision type may be provided to the collision overlap determination904. The collision overlap 904 generates a full overlap signal or a 50percent overlap signal. Also, various levels in between full and 50percent overlap may be generated. After the collision overlapdetermination, a driver classification determination is set forth inblock 906 and a passenger classification determination is set forth inblock 908. The driver and passenger classification correspond to weightclasses of the various passengers or drivers along with their belted andunbelted status. The seating position of the driver is determined inblock 910 and the seating position of the passenger is determined inblock 912. Each of these conditions may be used in operation of thedeployment handler.

Referring now to FIG. 16, a method similar to that set forth in FIG. 10is illustrated. Steps 1000-1018 correspond directly to those set forthin FIG. 10 and will not be repeated. Thus, the present discussion willcommence with step 1020.

In step 1020, if the confidence factor threshold is met forpre-collision activation, step 1022 is executed. In step 1022 theoptimal restraint activation values for the front occupants aredetermined. In step 1024, various adaptive restraints are deployed in apre-collision mode. This method ends in step 1025. Referring back tostep 1014, if the pre-collision classification does not call for apredeployment, the collision is confirmed with vehicle mountedaccelerometers in step 1026. In step 1027, if the collision is notconfirmed, step 1002 is repeated. In step 1027 if the collision isconfirmed, step 1030 is performed in which the adaptive restraint systemis deployed in post-collision mode. After step 1030, step 1040 ends theinvention.

Referring back to step 1020, if the confidence factor threshold is notmet for preactivation, then step 1028 is performed to determine if theconfidence factor threshold is met for pre-arming. If the threshold forpre-arming is not met, step 1026 is performed. If the confidence factorhas been met for pre-arming, step 1050 is performed. In step 1050, therestraint system is pre-armed and in step 1052 the collision isconfirmed with vehicle-mounted accelerometers. If the vehicle collisionis confirmed in step 1054, then adaptive restraints are deployed in apre-armed mode in step 1056. This process ends in step 1058. In step1054 if the collision is not confirmed the system returns to step 1002.

Referring now to FIG. 17, the deployment determination stage 802 is setforth in further detail with respect to the flow chart. In step 1102,the deployment determination is set forth. In step 1103, various targetinformation is obtained from the pre-crash sensing system. In step 1104the airbag deployment met flag is set to no, the EMR deployment set flagis set to no, and the critical time is set to 999.99 ms. In step 1106the system checks to see if all targets are evaluated. When all targetshave been evaluated, step 1108 is performed. In step 1108, if the EMRdeployment is met or the airbag deployment is met, step 1110 is executedin which if the airbag deployment is met then a critical time minus theairbag time to deploy time is set to the wait time. In step 1110, if theairbag deployment flag has not been set, step 1114 is executed, whichsets the wait time equal to the critical time minus the EMRTime-To-Deploy (TTD) time. Otherwise, step 1112 is executed, which setsthe wait time equal to the critical time minus the airbag (AB) TTD time.The airbag time to deployment and EMR time to deployment time are set to40 ms prior to impact and 250 ms prior to impact in this example. Aftersteps 1114 and 1112, step 1116 starts a timer. If the timer is less thanthe wait time, step 1118 is again executed. In step 1118, if the timeris greater than or equal to the wait time or the EMR deployment time hasnot been met or the airbag deployment time has not been met in step1108, step 1120 is performed in which the airbag deployment flag is met,the EMR deployment flag is met, and the critical target impact speed isoutput. The system ends in step 1122.

Referring back to step 1106, if all the targets have not been evaluated,various information is obtained. In step 1124, if the target equals avehicle and the detect status is mature and the impact confidence isgreater than the impact threshold and the overlap is greater than theoverlap threshold and the angle is less than the angle threshold, step1126 is executed in which the relative speed is compared to anelectro-mechanical retractor activation speed threshold and the time toimpact minus the electro-mechanical retractor time to deployment iscompared to a process time. In step 1126, if the relative speed isgreater than or equal to the EMR speed threshold and the time to impactminus the EMR time to deployment is less than or equal to the processtime, step 1128 is executed in which the EMR deployment met flag is setto yes. If step 1126 is not true, and after step 1128, step 1130 isexecuted in which a relative speed is compared to an airbag deploymentspeed threshold. If the relative speed is greater than or equal to theairbag deployment speed threshold and the time to impact minus theairbag time to deployment is less than or equal to the process time,step 1132 is executed in which the airbag deployment met flag is set toyes. After step 1132 and step 1130 being false, step 1134 is executed inwhich the electro-mechanical retractor deployment met flag and theairbag deployment met flag are determined. If either one of these isyes, step 1136 is executed, which compares the time to impact to acritical time. In step 1136, if the time to impact is less than or equalto the critical time, then step 1138 is executed in which the criticaltime is set to the time to impact and the critical object is set equalto the object. In step 1124, step 1134 and step 1136, if these inquiriesare no, and after step 1138 step 1106 is again executed.

Referring now to FIG. 18, a method for operating the device activationstage 804 of FIG. 14 is illustrated. In FIG. 18, the system starts instep 1200. In step 1202, various information about the vehicleconditions is determined. The target with collision information isdetermined, airbag deployment met flag is obtained, the driver size isobtained, the driver buckle status is obtained, and the driver seattrack position is obtained. In step 1204, if the airbag deployment hasbeen met, the restraint level is determined in step 1206 from the lookup table. Restraint levels may be set at various numbers of levels. Inthis example, levels 0-16 are set forth. In step 1208, the airbagigniter 1 delay time is returned from a look up table associated withrestraint control module. In step 1210, the delay timer is activated. Instep 1212, if the igniter delay time is greater than the delay time fromstep 1210, the delay timer is incremented in step 1213, and step 1212 isagain executed. If the igniter delay time is less than or equal to thedelay time from step 1210 the airbag igniter 1 is deployed in step 1214.After a negative return from step 1204 or the completion of step 1214,the system ends in step 1216.

While particular embodiments of the invention have been shown anddescribed, numerous variations and alternate embodiments will occur tothose skilled in the art. Accordingly, it is intended that the inventionbe limited only in terms of the appended claims.

What is claimed is:
 1. A method of operating a restraint systemcomprising: deploying an airbag prior to a collision in pre-collisionmode in response to a pre-crash sensing system output signal including apredicted time to impact; activating active vents based on the predictedtime to impact; confirming a collision using vehicle accelerationsignals, wherein the collision is confirmed at an elapsed time thatdiffers from the predicted time to impact; adjusting the predicted timeto impact based on the vehicle acceleration signals; and controlling theactive vents according to the adjusted predicted time to impact.
 2. Amethod as recited in claim 1 wherein controlling the active ventscomprises controlling the timing of an airbag vent.
 3. A method asrecited in claim 2 wherein the timing of the vent is determined inresponse to an occupant characteristic.
 4. A method as recited in claim2 wherein the timing of the vent is determined in response to a seatposition.
 5. A method as recited in claim 1 wherein the airbag comprisesa dual stage airbag comprising the first stage and the second stage witha means to control time delay between the two stages.
 6. A method asrecited in claim 1 further comprising monitoring a seatbelt status andwherein controlling the active vent comprises controlling the inflationalso in response to the seatbelt status.
 7. A method as recited in claim1 further comprising determining an occupant characteristic and whereincontrolling the active vents comprises controlling the active vents alsoin response to the occupant characteristics.
 8. A method as recited inclaim 1 further comprising classifying a collision into a collisionclassification in response to a pre-crash sensing system.
 9. A method asrecited in claim 8 wherein the block of classifying comprises scanning afrontal zone with a pre-crash sensing system.
 10. A method as recited inclaim 8 wherein the block of classifying comprises determining arelative velocity of a threat.
 11. A method as recited in claim 1further comprising determining a confidence factor threshold and apre-crash collision confidence factor and wherein deploying comprisesdeploying in response to comparing the confidence factor and theconfidence factor threshold.
 12. A method as recited in claim 11 whereinif the confidence factor is not above a threshold, determining acollision in response to a vehicle accelerometer and wherein controllingthe restraint system in response to the vehicle accelerometer in apost-collision mode.
 13. A method of operating an airbag having acontrollable vent comprising: deploying an airbag prior to a crash inresponse to a pre-crash sensing system output including a predicted timeto impact; operating an airbag vent to control a rate of inflation;determining a crash severity; determining occupant information;confirming a crash using vehicle acceleration signals wherein the crashis confirmed at a point in time other than the predicted time to impact;adjusting a predicted time to impact based on the vehicle accelerationsignals; and operating the airbag vent in response to confirmation ofthe crash, the crash severity, the occupant information, and theadjusted predicted time to impact.
 14. A method as recited in claim 13wherein determining occupant information comprises determining belted orunbelted status.
 15. A method as recited in claim 13 wherein determiningoccupant information comprises determining a weight range.